The present invention is particularly directed to an alternator regulator having output monitoring and limiting controls, and particularly to a regulated alternator having current limit means and a loss of parameter monitoring means.
The output of alternators may be automatically regulated in accordance with certain sensed parameters of the alternators. Engine driven alternators for example generally include voltage regulators for monitoring, establishing and maintaining a constant output voltage with variation of load speed and the like. In such regulated systems, current limit systems may be necessary and provided to prevent the output current from rising above a preselected maximum level. Generally, current sensor units detect excessive current conditions, out of phase currents and the like for monitoring the significant operation of the regulator. Such systems do not however provide a means for accurately detecting a fault in the sensor units or circuits such as a break in the sensing lead, a loose terminal in the sensing circuit or like fault which effectively opens the sensing circuit. The sensed voltage will drop to zero when an open circuit condition exists in the sensor unit.
With the regulator driven from a separate power supply such as a permanent magnet generator, the regulator responds to the output of the voltage monitoring unit regardless of the actual source of the monitoring signal. In particular, a break in a sensing lead or a loose connection of a sensing lead appears as a low voltage condition. The voltage sensor unit signal then demands increased excitation of the alternator in an attempt to increase the voltage output of the alternator. This will increase all of the voltage and available current with a disasterous consequence within the main alternator and/or the connected loads. Full forcing operation within the regulator and on the exciter may also create damage within such components.
If the regulator sense a zero voltage condition, the prior art generally immediately responds with means to shut down the alternator.
Although such a system may be used to guard against abnormal current, the prior art systems do not provide normal voltage regulation under certain conditions and current regulations under alternate conditions while maintaining appropriate current limit response in the event of a damaging current failure. Thus, the prior art systems do not appropriately distinguish between the various conditions which can create an essentially zero output voltage to the regulator, namely, a short circuit condition of the alternator and alternatively an open detection circuit both of which signal the regulator to increase the output of the alternator, with appropriate control action depending upon the source of the fault.